Virology 2 PDF

2 BY ABDULFATAH ALBAKKOSH Enteroviruses • Enteroviruses are RNA viruses that belong to the Picornaviridae family and are members of group IV Baltimore (+ssRNA). • The enteroviruses were divided into four categories, namely, polioviruses, Coxsackie A viruses (CA), Coxsackie B viruses (CB), and echo...

2 BY ABDULFATAH ALBAKKOSH Enteroviruses • Enteroviruses are RNA viruses that belong to the Picornaviridae family and are members of group IV Baltimore (+ssRNA). • The enteroviruses were divided into four categories, namely, polioviruses, Coxsackie A viruses (CA), Coxsackie B viruses (CB), and echoviruses. • A Coxsackie A virus, a Coxsackie B virus, and an echovirus are all called non-polio enteroviruses. Most people who get these viruses don't get sick, or they only get a little sick. Some people can have serious problems, like babies and people with weak immune systems. Picornaviridae Echoviruses (+ssRNA) non-poliovirus Coxsackie B viruses Polioviruses Coxsackie A viruses Enteroviruses Enteroviruses • A Coxsackie A virus, a Coxsackie B virus, and an echovirus are all called non-polio enteroviruses. Most people who get these viruses don't get sick, or they only get a little sick. Some people can have serious problems, like babies and people with weak immune systems. • Enteroviruses spread through the fecal-oral route. Enteroviruses • Coxsackie viruses are often associated with human hand, foot, and mouth disease. Additionally, Coxsackie B viruses may result in a fever, a slight rash, and mild upper respiratory tract (URT) illness. • But these viruses may also cause more severe disorders, such as myocarditis; meningitis; and pancreatitis. • Echoviruses are a cause of many of the non-specific viral infections. It is mainly found in the intestine, and can cause nerve system disorders. • Hand, foot and mouth disease by Coxsackie viruses Poliovirus • Morphology • Family Picornaviridae. Icosahedral ,non-enveloped. • Genome: (+)ssRNA . • There are three serotypes of poliovirus, and various laboratory techniques can differentiate them. Poliovirus transmission • The faecal-oral route of transmission is more prevalent than the respiratory route for the spread of poliovirus. • The virus is spread by the faeces of infected people. In 95% of cases, viremia is transient, and the infection is asymptomatic. • The continued viral replication induces secondary viremia and leads to the development of minor symptoms such as fever, headache, and sore throat. Disease • Poliomyelitis: • Poliomyelitis is a rare paralytic illness. When a virus penetrates the CNS and replicates in motor neurons in the spinal cord, brain stem, or motor cortex, it causes short or long term paralysis. • Rarely, paralytic poliomyelitis causes respiratory failure and death. Poliovirus infects nerve cells lead to paralysis Immune response: • There is an initial specific IgM response, followed by IgG. • IgG in the blood and IgA on mucosal surfaces both play a function in avoiding re-infection. However, antibodies directed against one serotype may not provide protection against the other. vaccination against the poliovirus • There are two forms of poliovirus vaccine: live attenuated (OPV) and inactivated (IPV). Albert Sabin successfully developed the OPV (also known as the Sabin vaccination) in 1961. • Jonas Salk developed IPV and it became widely used in 1955. • Typically, vaccination timetables consist of four doses: two months, four months, six to eighteen months, and a booster dose between two and five years. • According to the World Health Organization, the two vaccinations have eliminated polio in most countries and reduced the number of infections per year from 350,000 in 1988 to 359 in 2014. • OPV= Oral Poliovirus Vaccine • IPV= Inactivated Poliovirus Vaccine Oral Poliovirus Vaccine • Oral Poliovirus Vaccine induces blood poliovirus antibodies against all three serotypes. Oral Poliovirus Vaccine induces a mucosal immune response in the intestines' mucous membrane. These mucosal antibodies inhibit the replication of poliovirus in the intestine. Advantages of Oral Poliovirus Vaccine 1. OPV is a vaccine that is administered orally. 2. Without sterile injection equipment or qualified health personnel, volunteers may administer it. 3. There is no cost associated with the vaccination. 4. It is completely safe, effective, and resistant to OPV for a long time. There are three poliovirus serotypes. Following vaccination, the vaccine virus replicates in the stomach, excretes in the faeces, and may be transmitted to other (uninfected) people nearby, resulting in passive immunization of unvaccinated individuals. Disadvantages of Oral Poliovirus Vaccine: • The live attenuated vaccination virus in OPV can cause paralysis in rare cases (1 in 2.7 million). People with immunological deficiencies may develop vaccine-associated paralytic polio. • Rarely, the vaccination virus may genetically mutate and begin spreading throughout a population. Vaccine-derived polioviruses are circulating in the population. Inactivated polio vaccine (IPV) • IPV, like OPV, includes all three poliovirus serotypes. • IPV is administered through a leg or arm injection. • IPV's advantages include the following: 1-Because it is a non-live vaccine, there is no danger of vaccination-associated polio paralysis. 2-IPV induces a stronger protective immune response than OPV does in the majority of individuals. Disadvantages of IPV • 1-IPV decreases intestinal immunity. • Defects in IPV immunity allow wild (infectious) poliovirus to remain in the intestine and be excreted in faeces, which might infect other individuals again. • IPV is more than five times the cost of OPV. • Vaccine administration involves qualified health workers and sterile injection equipment. Lab.diagnosis Poliovirus can be found using an electron microscope in the throat, faeces, and occasionally cerebrospinal fluid (CSF) specimens, or by isolating the virus in cell culture or its genome using polymerase chain reaction (PCR). Lab.diagnosis • Patients' blood samples may be tested for IgM and IgG antibodies by ELISA. • Serology may be useful in determining whether a patient has paralytic poliomyelitis, especially if the patient has not been vaccinated. • A serum sample should be taken early in the illness process, and a second sample (verified) should be obtained at least three weeks later.